It's possible that your oil pressure gauge isn't working. I think mine is busted. I used to have a normal gauge cluster and the oil light never came on at all, so I figured I had good oil pressure. Then I switched to an SR5 style cluster and the oil pressure needle just barely moved from zero at like 4000 rpm, and now it stopped moving all together, so I think my gauge is bad. I believe there is a way to test the gauge, and I think it's by grounding the oil pressure sender wire to the frame or something, not totally sure.